The tribe wants to intervene for the "limited" purpose of asserting its ownership of the Osage mineral trust, according to a motion filed on Wednesday. The tribe says neither the Cobell plaintiffs nor the federal government can represent its interests.

"Because the plaintiffs directly contest the Osage Nation's position regarding ownership of mineral revenue, the only party left to represent the Osage Nation's interests is the United States," the tribe's attorneys wrote in the motion. "But the United States has already shown that it will not be an adequate advocate for the Osage Nation's interest in the Osage mineral income."

Robertson convened a trial on June 9 to put a dollar figure on the government's failure to account for the Individual Indian Money (IIM) trust. The trial enters its eighth day today and is likely to end next week.